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The authors analyze the hypothesis that women reared without brothers experience higher educational aspirations than women reared with brothers. Some support is offered for the hypothesis. If there is such an effect, it will have more impact in the future as more sex-homogeneous sibling sets will result because of the trends toward reduced family size. Finally, the authors offer the tentative assertion that being raised in a family of all girls has a salutary effect on girls' socialization toward educational achievement.